VTC Question

[Chris_F]

I'm looking at getting some aftermarket cams for my k24a3 (Accord Euro). Something like Brian Crower Stage 2's, Blueprint Stage 2's etc.

My question:

Should I bother replacing the VTC gear to the 50 degree one from the DC5r?

I know with some cams it's not safe to use the full 50 degrees anyway so is the 25 degree VTC gear really that bad? I'm thinking the 25 degree mechanical limit could be a good safeguard with aftermarket cams.

Opinions? Advice?

Cheers,
Chris

[Benson]

lower VTC is safer for any engine

Ill stick with stock VTC

[fatboyz39]

I'm looking at getting some aftermarket cams for my k24a3 (Accord Euro). Something like Brian Crower Stage 2's, Blueprint Stage 2's etc.

My question:

Should I bother replacing the VTC gear to the 50 degree one from the DC5r?

I know with some cams it's not safe to use the full 50 degrees anyway so is the 25 degree VTC gear really that bad? I'm thinking the 25 degree mechanical limit could be a good safeguard with aftermarket cams.

Opinions? Advice?

Cheers,
Chris

If upgrading cams, i would keep it stock 25 VTC. With stock cams then 50VTC is ok but i heard that running 50VTC you MIGHT get some valve to piston contact. We only ran stock k24 vtc and they make some decent power.

Will let the K-series expert reply to this.

[Chris_F]

thanks for the input so far guys, really appreciate it.

If anyone has any reccomendations for an after market cam let me know.

At the momeny I'm tossing up between Blueprint Stage 2 or Brian Crower Stage 2.

[TODA AU]

Quoted from Hondata.com website...
http://www.hondata.com/tuning_k24a2_tsx_engine.html

"The biggest gift Honda has given to tuners of the K series engine is the VTC mechanism. Located on the end of the intake camshaft the VTC mechanism, via hydraulics allows 25 [crank] degrees of continuous movement on the TSX and 50 degrees on the RSX. For all you old school tuners lurking out there still changing the jets on your carburetors, who think you have to junk the VTC mechanism and go with a good old fashioned cam timing wheel, think again. In every naturally aspirated engine K20a and K24 engine we have tuned, the intake cam needs to be rotated through 25-30 degrees between peak torque and peak power. For emissions, the ability for Honda to rotate the cam to zero at idle to dial out all overlap makes for a very clean engine with no need for EGR. EGR porting is on place on the head but is blocked off.

25 degrees of cam movement is fine for a stock TSX engine but completely inadequate for modified engine with as little as race headers and intake. A stock engine needs no more than 20 degrees of cam moment on the high cam. A well modified setup needs no less than 25 degrees on the high cam. Take a good look at the modifications we made to the VTC mechanism. If you have a TSX you are going to need these changes. Although you could probably purchase and bolt on an RSX VTC mechanism for 50 degrees travel, there is less valve to piston clearance on the TSX pistons. Our measurements suggest 45 degrees maximum cam movement is much safer. Allowing the full 50 degrees movement leads to a greater risk of valve to piston contact should you accidentally mis-shift and over-rev.

http://www.hondata.com/images/tsxtuning/vtc_small.jpg

TSX VTC mechanism showing material to be removed to increase the cam advance from 25-45 degrees"

If you're handy with the tools, this is a cost effective alternative.

Regarding cams to use...
It really depends on the rest of the combination & the engine management that's going to run the thing.

[Chris_F]

Thanks Adrian. I've read that article before. The big advantage of the 45 degree VTC seems to be with the stock cams since they have fairly mild duration.

From the research I've done so far it seems that some of the more agressive aftermarket cams make best power with only 30-35 degree maximum VTC advance. The Blueprint Stage 3's for example can only have a maximum of 30degree VTC becuase of piston to valve clearances. 25 degrees would make things nice and safe and I don't mind sacrificing a few kw's for piece of mind.

Could you PM me some details about the Toda Spec C cams you suggested? Do you know what sort of VTC advance usually works best with those cams on a k24?

my setup for reference:
GruppeM intake
Maxim works exhaust manifold
metal cat
2.5" exhaust

will be tuning with a Vipec V88 (full i-vtec control)


In short - aggressive cams require less VTC anyway so why not just spend the money on a nice set of cams and forget about the 50degree VTC?

[EG5]

Im running 50 degree VTC on my k24a3 with buddyclub n+ cams package
8100rpm with stock bottom end
Never have any problems as its not set to 50 degree VTC on the kpro

You dont need 50 degree VTC if you dont run aggresive cams.
My cams is only entry level.